2 hot rads near the boiler. All others cold.

[reluctanthandyman1]

Can anyone advise? My mum has a newish Worcester Bosh combi boiler located in the kitchen. The 2 rads closest to it are nice and hot (these are located in the bathroom above the kitchen).
However the next rad along the line in the back bedroom is cold, and all rads thereafter are cold (3 cold rads in total).
What could be causing this? The rads are all fairly old.

 

[45yearsagasman]

Are they all turned on?

 

[reluctanthandyman1]

All are turned on. The flow pipe is hot right up to the trv on the back bedroom rad (all trvs are turned up full). After this point the flow pipe (and return pipe) is cold.

 

[D_Hailsham]

All are turned on. The flow pipe is hot right up to the trv on the back bedroom rad (all trvs are turned up full). After this point the flow pipe (and return pipe) is cold.

Have you bled the rads? This should be done with the boiler off and the water cold. Do all rads, starting with the downstairs ones.

Remove the TRV heads (no water will come out) and check that the pin in the top of the valve body will go down when pressed and spring up when released. Also try tapping the side of the valve body with a hammer - the valve may have stuck closed. If this doesn't solve the problem, check that the valve at the other end of the rad is not shut. If it is, open it about half a turn and check what happens.

 

[reluctanthandyman1]

Thanks for the replies guys.
All rads have been bled. I do need check the lockshield valves to make sure they are open - I assumed that they would be.
It'll have to wait until I go back over to my mum's house.
I was just wondering what the most likely scenario is that would be causing the problem - is it a likely sludge blockage, or an air blockage, or a problem with the pump?

By the way - as there are so many different types of trv headcovers, are there various ways of removing them or do they all just "pull off" once you have fully opened them up?

 

[45yearsagasman]

The 1st thing to check is that tha rads are on and that includes all valves, lockshields included.

 

[D_Hailsham]

By the way - as there are so many different types of trv headcovers, are there various ways of removing them or do they all just "pull off" once you have fully opened them up?

Most of them are held on by a large knurled round nut which connects the head to the metal body. You turn it anticlockwise, looking down from above. Some have a screw to hold the head on